We have made significant progress in defining the use of immunoglobulin (Ig) variable region genes (V genes) in chronic lymphocytic leukemia (CLL). Prior studies suggesting restriction in the Ig V gene repertoire have been extended, revealing that the Ig expressed in CLL possibly are selected for their ability to bind multiple self-antigens with low affinity. We generated transgenic mice with B cells that express such polyreactive human IgM and found that these cells can differentiate into marginal zone (MZ), memory-type B cells. Such MZ B cells share gene expression profiles with that of CLL cells. These and other newly developed transgenic mouse models of CLL will allow us to evaluate whether Ig receptor signaling plays a role in leukemogenesis and/or disease progression. Recent studies have revealed that patients with CLL cells expressing mutated Ig have a more indolent clinical course that those with CLL cells that express unmutated Ig genes. Gene expression studies revealed that CLL cells expressing unmutated Ig could be distinguished from the more indolent type through the differential expression of a relatively small subset of genes, one of which encodes ZAP-70. We found that CLL cells that express this protein tyrosine kinase have more proficient signaling via the B cell receptor (BCR) complex than CLL cells that do not express ZAP-70. Transfection studies using adenovirus vectors encoding wild type or mutant forms of ZAP-70 are helping to resolve whether ZAP-70 plays a functional role in BCR signaling that can serve as a therapeutic target in this disease. Finally,work on this project has led to development of strategies for inducing anti- leukemia immune responses via the use of CLL cells that are activated via CD40-ligation. Phase I and early phase II clinical trials using recombinant adenovirus vectors encoding a recombinant CD40-ligand (Ad- CD154) are direct manifestations of work performed on this proposal. Further studies could enable us to refine this approach toward development of truly effective immune therapy for patients with this disease.